package leetCode;

/**
 * Created by liyong on 16/7/10.
 */
public class MaxProfit {
    public int maxProfit(int[] prices) {
      if (prices == null || prices.length < 2) {
        return 0;
      }

      //highest profit in 0 ... i
      int[] left = new int[prices.length];
      int[] right = new int[prices.length];

      // DP from left to right
      left[0] = 0;
      int min = prices[0];
      for (int i = 1; i < prices.length; i++) {
        min = Math.min(min, prices[i]);
        left[i] = Math.max(left[i - 1], prices[i] - min);
      }

      // DP from right to left
      right[prices.length - 1] = 0;
      int max = prices[prices.length - 1];
      for (int i = prices.length - 2; i >= 0; i--) {
        max = Math.max(max, prices[i]);
        right[i] = Math.max(right[i + 1], max - prices[i]);
      }

      int profit = 0;
      for (int i = 0; i < prices.length; i++) {
        profit = Math.max(profit, left[i] + right[i]);
      }

      return profit;
    }
}
